This invention relates generally to apparatus and methods for semiconductor package fabrication and more specifically to apparatus and methods for synchronous coverlay film removal and adhesive application to semiconductor support elements and the like.
In semiconductor manufacture, a single semiconductor die (or chip) can be packaged within a sealed package. The package protects the die from damage and from contaminants in the surrounding environment. In addition, the package provides a substantial lead system for electrically connecting the integrated circuits on the die to the outside world.
One type of semiconductor package 10 is illustrated in FIG. 1A. The package 10 includes a substrate 12 having a planar die attach surface or die site 22. A semiconductor die 16 is mounted to an upper surface of the substrate 12 on the die site 22. The die 16 is typically adhesively bonded to the substrate 12 with an adhesive layer 34. An encapsulating resin 38 encapsulates the die 16.
In addition to the die site 22 on the upper surface, the substrate 12 includes an opposing conductor surface 9 wherein conductors 18 are formed in a required pattern. A wire bond opening 26 in the substrate 12 provides access for bonding wires 28. The bonding wires 28 are connected to the conductors 18 and to bond pads (not shown) on the die 16. A glob top 40 is formed over the wires 28 for protection.
The semiconductor package 10 also includes an array of solder balls 14. The solder balls 14 are bonded to ball bonding pads 24 on the conductors 18.
As shown in FIG. 1B, the substrate 12 is initially a segment 32 of a support element 30. The support element 30 includes multiple substrates 12 (and thus multiple die sites 22). The support element is used to fabricate multiple semiconductor packages 10. The support element facilitates the fabrication process in that different operations, such as die attach and wire bonding, can be performed at the same time on each of the substrates. Following the fabrication of the semiconductor packages 10 from the support element 30, the support element is singulated into individual semiconductor packages.
The process for packaging semiconductor dice includes matching a die to each die site on the support element. The die is attached, using an adhesive, to the die site over the wire bond opening 26 so that the die may be electrically connected to the substrate. Currently available support elements typically include one or more substrates that are defective or non-functional, i.e., the substrates include xe2x80x9creject die sites.xe2x80x9d Individual substrates of a support element may be non-functional for a variety of reasons, such as faulty electrical circuitry of a substrate. Such defect substrates of the support element cannot be utilized to fabricate a functional semiconductor package but cannot be separated from the support element prior to processing of the other substrates on the support element. If the defective substrates are separated from the support element, such action necessarily limits the number of substrates that may be processed at one time using the separated support element. Thus, physical separation of defect substrates from the support element prior to fabrication of the semiconductor packages is not preferred.
When functional dice are attached to the xe2x80x9creject die sitesxe2x80x9d of the support element and further are processed, the resulting semiconductor packages are necessarily defective. This sacrifices functional dice, thereby increasing semiconductor package manufacturing costs and decreasing yields. To avoid the added cost (i.e., sacrificing functional dice), a xe2x80x9creject die sitexe2x80x9d on a support element could simply be skipped or omitted during the die attach process. Regrettably, omitting attachment of a die to a die site on a support element causes problems during the encapsulation process.
During the encapsulation process, liquid encapsulation material flows over and around the attached dice and substrates of the support element. If one or more bonding slots are left open, i.e., a die is not attached to a die site of the support element, the encapsulation material flows through the uncovered opening 26. When the encapsulation material flows through such openings, it contaminates dice adjacent and/or near the uncovered opening. This is known as xe2x80x9cbleeding or flashing.xe2x80x9d The bleeding of encapsulation material produces even more defective semiconductor packages, further increasing manufacturing costs and lowering yield. Moreover, bleeding of the encapsulation material may stick to the mold body and contaminate the next support element processed through the encapsulation machine.
In attempt to avoid (1) sacrificing functional dice by attaching the dice on reject die sites, (2) contaminating adjacent dice and mold bodies by omitting attachment of dice to reject die sites, and (3) processing support elements that include a minimal number of substrates due to prior separation of the defective substrates, the industry pays a premium price for support elements having no reject die sites. This also increases semiconductor package manufacturing costs.
Accordingly, there is a need for a process for making semiconductor packages using support elements having one or more reject die sites without contaminating adjacent dice and without destroying functional dice by attaching the dice to reject die sites. To this end, the present invention provides apparatus and methods for applying a cover member, such as a strip of self-adhesive film, to the reject die sites. The cover member covers the reject die sites prior to encapsulation thereby eliminating the risk of contamination of adjacent dice on a support element during encapsulation and preserving functional dice for use on functional die sites. Further, the apparatus and methods of the present invention apply with a predetermined amount of force exact lengths of adhesive film to the support element and synchronously remove the adhesive film""s coverlay film just prior to application of the adhesive to the support element.
According to the present invention, reject die sites on a support element are covered prior to the encapsulation process using the apparatus and methods of the present invention. More specifically, the apparatus and methods of the present invention synchronously remove a coverlay film from adhesive film, cuts and applies exact lengths of adhesive to reject die sites on the support element to act as a cover member thereon (or to allow for attachment of a separate cover member thereto). The apparatus and methods of the present invention may also be used to synchronously remove a coverlay film from adhesive film, and to cut and apply exact lengths of adhesive to functional die sites on the support element for attachment of functional dice thereto. The application of adhesive strips as cover members to reject die sites (or for attachment of a separate cover member thereto) virtually eliminates bleeding or flashing during encapsulation due to the presence of reject die sites while avoiding the need to sacrifice functional dice to cover such reject die sites. The apparatus and methods of the present invention further provide an efficient process for removal of the adhesive film""s coverlay film with the synchronous application of cover members to reject die sites of a support element.